Electron-tube amplifying apparatus



- May 24, 1927.

1,630,118 R. S. FISHER ET-ECTRON TUBE AMPLIAFYING APPARATUS Fne'd'Jume, 1925 :s sheets-sheet 1 rwentoz N www #uw y 2 .7 R. s. FISHER ELECTRON TUBE AMPLIFYING APPARATUS 3 Sheets-Sheet 2 Filed Ju1.v"6. 1925 .MOANMJ ma a.. ,n .1 MW n WW uw 19/ 1 1 n w A 1Qk .1.a vn. @www m am; Y RM A m, 8% UU 0 Y Q\ 10.

Patented May. 24, 1927.

UNITED STA-TE l 1,630,112;v PATENT OFFICE- y BOY S. FISHER,l F PHILADELPHIA, PENNSYLVANIA, ASSIGNOR TO'TIHHONS RADIO PRODUCTS CORPORATION, OF PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA;

iLECTRON-TUBE AMPLIFYING APPARATUS.

Application filed July 6,

invention relates broadly to electron tube amplifying apparatus and more partic- /ularly to an electron tube amplifying system which has a common energy supply circuit 5.for delivering power to the cathode, anode .and grid circuits of the amplifying system. One of the objects of my invention is to provide an electron .tube amplifier circuit employing a plurality of electron tubes in which the cathode heating circuits and the .anode circuits of the tubes may be supplied with energy from the usualhouse lighting: circuit without the employment of batteries.

lAnother object of my invention is to provide a circuit arrangement in an electron tube amplifying system by which the power circuits of the electron tubes ma be supplied with energy from the usual a ternating -current house lighting circuit with'substantially complete elimination of the hum of the alternating current in the amplifying apparatus. y A

Another object of my invention is to provide an arrangement of an electron tube am; plifying circuit'by which the proper biasing potential may be. derived for the grid. circuits of the several tubes, a proper value of` anode potentialy impressed upon the anodesv of the several tubes and an accurate value o.=` cathode heating currgnt delivered to the several tubes of the series with means disposed g in the. amplifying circuit lfor substantially eliminating any trace of alternating current hum in the amplifying circuit when the circuits are supplied from the usual source of house lighting current. Still another object of my invention is to providev a circuit arrangement for electronn tubes in rectifying and amplifying systems` in which the filament heating current of the several tubes and the plate voltage for the several tubes may be supplied from a resist. ance netV work in which rectified alternating current is iiowing.

A further object. of my invention is to pro- 7ide an electron tube system for an 'amplification circuit in which the output vcircuits of thc several tubes. and thebiasing potential for the grid circuits of the tubes are supplied froma series'circut in which isdi a resistance 'net work for proportioning' the proper energy supplyffor the different parts of the-circuit.

A still further object fxy mventionis to v,taken rom the resistance net work;

1925. serial No. 41,635'.

provide a circuit arrangement for a pushpull system of amplification whichimay be operated in combination with the electron tube circuits. of an amplifier for re roductlon of the signaling .energy at re atively largeamplitude without interference from hum normally present in the alternating current power supply from which the apparatus may-.be operated.

Still another object of my invention is to bprtn'fide an electron tube rectifying and am- 05 lifying system having a series circuit arrangement supplied from a single source of energy of any suitable characteristic for heating the cathodes, polarizing the anode's and blasing the grids. 4 70 A further object of my invention is to provide a rectifying and amplifying system constituted by a plurality of electron tubes with a series circuit for delivering power to, the circuits of a, number of the tubes while power may be independently. suppliedto the circuits of others of said tubes which may normally require larger power than is sup-l plied tothe first. mentioned tubes. I have selected for villustration of my in- 30 vention the adoption of the amplifying sys-y tem yto a radio receiving apparatus, although' it will be understood that' the amplifying system described herein is generally applicable ,to the detection and amplification of feeble electrical currents regardless ofthe function for which the system is utilized. -Lgf invention will be more 4fully understo by reference to the following specification, andthe accompanying drawings, in. 9 which: l -v'Figure 1 illustrates an amplification circuitarrangement employing 'the rinciples of my invention as applied to a. raio receiv-- ing system; Fig. 2 is a fragmentary portion 95 of the amplifying circuit showing one of the methods by which the'cathode heating" j energy is supplied from' the rectification circuit and the filaments of the several tubes protected against destruction; Fig. 3f illus- 100 trates the rinci le of my invention in con--A nection wit a p urality. of electron tubesin an amplification circuitwhere different values of late potential are supplied from taps Fig. 4 105 shows a modified form of amplifier' circuit wherein Separate resistance net worksA are provided foriobtaining Vthe high potential.

supply for the detector and amplifier tubes of the receiving circuit and wherein the plate current of the'last amplifier tube may be balanced against the filament currents of the preceding tubes; and Fig. 5 shows a method which I have devised for supplying power to the filament and plate circuits of electron tubes of a reetifying and amplifying system in combination with a push-pull amplifier connected in the output circuit of the rectifying and amplifying system for securing reproduction of the signaling energy at large amplitude without interference from the hum of the alternatingI current.

Heretofore in the art sensitive electron tube amplification apparatus when operated from a. source of alternating current has required that the electron tube circuits necessarily function below the point of maximum sensitivity in order that the normal hum of the alternating current will not offer undue interference with the received signals. By obtaining the convenience of operation of the amplifying circuits from a standard source of alternating current, it has been necessary to sacrifice sensitivity of the tube' circuits and accordingly when the amplifying system is utilized in a radio receiving apparatus the range of the receiving` set as compared to that obtainable in a battery supplied receiving set is usually considerably reduced. There are many problemsin designing a radio receiving circuit which may be efficiently operated from the usual d source of alternating current house lighting system and it will be apparent that the periodic changes in the direction of current flow may introduce a constant source of interference in the sensitive electron tube eircuits unless sp-ecial revision is made for eliminating the hu,... Proposals heretofore made in the art for operating electron tube apparatus from the alternating current house lighting system have generally utilized a circuit arrangement following the Well-known principles of battery operated sets where the alternating current is introduced into the set at points normally occupied by batteries with the cathodes parallel connected. I have found that this is not a desirable arrangement and that in order to overcome. undesirable interference it is necessary to rearrange and modify the circuits of the amplifying system as is shown in thev accompanying drawings.V

I provide a current supply system for connection to the alternating current-power supply, consisting of a transformer having a primary winding and secondary windings arranged in different ratios for developing a relatively high potential which is rectified by a unilateral tube circuit for delivery to a resistance net work. One of tht-,secondary windings may be arranged to supply cathode heating energy to `the rectifier, while still another secondary winding may be arranged for supplying alternating current direct to the cathode of the final tube of the systcn'i. The direct current network is so arranged that plate voltages of various potentials may bc obtained from a single source of direct current. The filament heating current also may be obtained from the same. single source of direct current. The resistance network from which the plate supply obtained is connected in series with the filament circuit of several of the tul'resand therefore the amount of current drawn from the direct current source is a minimum which is very desirable when rectified alternating current is used. or even when av generator is cmployed` as the filter system can be made much smaller in size than it. would normally be if operated upon larger current by reason of the low current value existent in the anode circuit of the rectifier tube. The life of the rectifier tube may be considerably prolonged. 'hile I have illustrated a single wave rectifier I desire that it be understood that full wave rectification may be employed without departing from my invention. filiere a tube is used in thc amplifier which will have greater power capacity than the preceding tubes requiring far greater plate current than the other tubes. its plate to filament circuit. is placed in series with the filaments of the preceding tubes. This is a very economical method. so far as current consumption is concerned. and it is desirable in that it allows a relatively small filter system to be used in the hum eliminating arrangement. Only singlewvave rectification is necessary for the elimination of hum inthe amplifier of my invention. or a single source of direct current with the current values at. a minilnum may be used by reason of the particular circuit within the amplifier. The filament of the tube in the last stage would usually require a much heavier current than the preceding stages and therefore can be supplied from a separate source.

In some arrangements of electron tubes in an amplifying circuit the filament to plate circuit may draw less current than is required for the filaments of the preceding tubes. In this event a. resistance is connected in shunt with the filament and plate of the last tube with the value of the resistanees so Selected that the proper current flows in the plate circuit of the last tube. This resistance may also be suitably tapped to enable different potentials to be derived therefrom to furnish the plate currents of the preceding stages. In applying the principles of my invention to a radio receiving apparatus the entire control of the power supply to the several circuits may be effected by means of a rheostat in the filament circuit of the rectifier tube system. A suitable filter is employed in connection with the rectifier sys- Btl lou

from the grids ofthe several tu es.

. The output circuit of through coupling 1,630,118 teni4 for blocking the alternatin current plying the filament circuits of the rectifier The biasing potential for the grids of the sev-v eral tubes is obtained froin'taps taken from e the grid returns of the radio-,frequency amplifier tubesA and the audio-frequency ainplitrom being modulated by the low frequency luie current, the cathode winding for the fier tubes to pointsin the filamenti circuit more negative than the cathode of the par,n ticular tube of the series. I may also provide an inde endent resistance and capacity network in tie amplifying circuit 4forsupplying plate voltage independently to the detector and aniplifiertubes. This arrangementoperates to further eliminate any A Ahum from the rectifying and amplifying'circuits.

Referring to the drawings in more detail reference character l designates an antenna system at a radio receiver connected to ground 2. and including` a suitable' coupling system 3 in circuit therewith tuned by condenser prise twostages of radio frequency amplific-ation constituted by tubes 5 and e, a detectr'7 andan audio frequency amplifica: tion circuit constituted bytubes 8 and 9. tube `is interlinked with the input circuit of tube '6 through a coupling transformer" 10. The input circuit of tube 6 istuned by means of condenser 1l. The output circuit of tube 6 is coupled to theD input circuit of the detector tube 7 transformer 12. The inputcircuit of the detector-tube 7 is tuned by means of variable condenser 14."A The detector circuit of tube 7 includes the grid condenser -and grid leak 15. '-The circuits of the ai'idiov frequency amplifier constituted by tubes 8 and 9 are couple-d by means .of audio frequency transformers, 16 and 17, each of the elect-ron tubes including a cathode or filament 5, 6a, 7 a, 8a and 9a. The cathodes 5, 6, 7a. and 8@L are connected lin series across which is sli-unted the protective resistance 18 network constituted` onda-ry windings 26, 27

with a resistance sistance units 19 2t'and 22 shunted The resistance and which is disposed in series and 20 with condensers thereacross as4 shown.

. capacity-net work' issupplied with'genergy' through the series filament circuits from the rectification circuit constituted b tube 2 3. v:Phe power sup ly apparatus includes a power transform r 24 having primary windingf25 which is connected to the usual alternating current' house lighting circuit. The transformer 23 vhas a plurality of secand 28. `The wind ing .27 is arranged to supply cathode heating energy to the rectifier tu 23 under control of the rheostat 29. The hi h potential siipply to the rectifier 23 `is erived from the winding 28 which connects to the filter circuit constitutedby choke coils 32 and condensers and 3l and 33. The reason for providing separate; secondary windings for sup- 1. The receiving circuit may coin-v e 23 and the filament'circuit ofthe final rectifier tube being at a high potential above ground. The positive terminal of the direct current supply is designated at 34, while the negative terminal ofthe direct currentl supply circuitis designated at 3 5. In order C' to secure a proper value of 'plate voltage for the detector tube 7 aresistanceG unit 36 is connected between -the terminal 34 and the output circuit of the tube 7. 'A conthe winding for the' cathode of the final amplifier-tube must have' the lowest potential above ground as posdenser 37 is Shiinted across thcoutput vcir.

cuit of the detector tube 7 for by-passing the radio frequency current component. The hi gh potential supply 'foi'.the output circuit of the tubes 5', 6 and 8 is obtained by. a tap taken from connection 38 in the resistance and capacity net work.

A Aresistance 39 isprovided connected be- ,tween aV point inv the series cathode circuit and a midpoint in a bridging resistance 40 across `the cathode 9a for establishingr a ncgative bias on the grid of the last tube. A

number of tubesot' the series iiiay have their rectified alternating cathodes energizedy by current, 'while the cathode 9a of the final stage of amplification is represented as being supplied froiii the secondary winding 26 through the leads 4l, by alternating current. The plate of tube 9 has the full output voltage of the rectifier tube it less the drop due toM circuit of tubes 5, 6, 7 and 8. The output circuit of the tube 9 is represented at 4 2 and may connect to any desired forni of responsive device or may lead through further stages of amplification.

' The several tubes indicated at. 5, 6, .7 and 8 which have their cathodes 5, 6a, 7a and 8a 23 impresse-d upon the series filament l in series, inay be protected by connectinga resistance 18 across the series cathode'circuit as indicated in Figs. 1 and 2. This resistanc-e protect-s the filaments of the tub-esin the event. that. the load is cliangedby. renioving one ,of the tubes. Then a tube -is' rcL moved a sudden rush of current occurs on tubes toburn' he resistance 18n placed across thc tubes, the detector and the first tube of tlic audio amplifier operates to absorb fiuctuations in energy and protects the ca tliodes. I

Fig.' 4 the last tube 9 have also' illustratedin high resistance -14 of the series as having a and a shuntiiig capacity 43 arranged in the ehlo'ck' any variation from the grid -and. to'

input circuit serving as a filter to' cycle AC protect the input transformer against any accidental heavy rush of current or excessive current in the grid; circuit of this tube. Such instantaneous rise of current resulting for example, by the shorting of the grid and plate electrodes might permanently destroy the operating efficiency of the amplifier. In order to secure the desired negative` potential for biasing the grids of' the radio frequency amplifier tubes 5 and 6 and the audio frequency'amplifying tube 8 connections are taken from taps in the filament circuit to the grids of' the tubes at points which are more negative than the cathodes of each of the tubes. That is to say, the control electrode in tube 5 is connected to a point 51 in the series cathode circuit which point is more negative than the cathode 5a. The control electrode of tube 6 is connected to a point 52 in the series cathode circuit which point is more negative than the cathode 6a. The control electrode for tube 8 is connected to a point 53 in the series cathode circuit which is more negative than the potential of the cathode 8, By selecting a proper point in the series cathode circuit an exact operating pqtential may be obtained.

In Fig. 3 of the drawings, I have illustrated the arrangement where the single source of direct current across the terminals 34 and 35 energizes the cathodes 5, '63, 7, 8 and 9a connected in series with the resistance capacity net. work comprising resistances 19, 2() and 49 connected in seriesrwith the cathode circuit. Condenser-s 21, 22 and are connected in shunt with each of the sections or portions of' the resistance net work 19, 20 and 49. Taps are taken at. points;

38, 49 and 55 for obtainingr the desired anode operating potential for the receiving system.

In Fig. 4, I have shown a complete radio receiving system embodying the principle ofmy invention where the entire control is effected by means of rheostat 29 in the cathode circuit of rectifier tube 23. The final stage of audio frequency amplification is shown having its cathode 9a heated from a source of alternating current delivered from secondary winding 26 as distinguished from the direct current operation of the cathodes 5. 6, 7a and 8 of the tubes 5, 6, 7 and, 8 respectively. The input circuit of the .tube 9 is provided with filter paths 43 and 44 for blocking the alternating current from the grid. I have shown a high frequency choke coil 56 in the rectifier circuit and a fuse 57 also disposed in the rectifier circuit for pro- (ill tecting the rectifier in the event that a condenser or portion of the apparatus becomes short circuited.

In Fig. 5 of the drawings I have illustrated the application of my invention to a push-pulll amplification system connected to the audio frequency circuit of .the amplifier. The push-pull amplifier tubes are represented by'reference characters 58 and 59 having cathodes 58a and 59a respectively. The input circuit for the push-pull amplifier 1s illustrated as including a transformer 60 having secondary windings (il andwGzZ connected in the respective tube circuits. The outputenergy from the push-pull amplifier is delivered through a transformer (i3 having primary windings 64 and 65 and a secondary winding 66. A single source of direct current supply is provided between terminals 34 and 35 serving to impress direct current on the cathodes of' tubes 5, 6, 7 and 8 in a circuit which includes the plates of the pushpull amplifier consisting of tubes 58 and 59 and the plates of`tubes 5, 6, 7 and 8. With this combination the plate current of the push-pull amplifier tubes 58 and 59 is mainof' approximately half the current required by tubes 5, 6, 7 and 8. The combination of thetwo plate circuits operating together equals the filament current of tubes 5, 6, 7 and 8 and therefore can be connected in series with these tubes. .The cathodes 58a and 59 may be operated from a source of alternating current derived from winding 26 as heretofore described. The common input circuit for the push-pull amplifier is connected` between a mid-point on the shunting resistance 40, regulating resistance 39, and hum 'eliminating circuit 44 and 43 with a mid-point between secondary windings 61 and 62. The operation of the amplifying circuit is maintained free from hum of the alternating current supply. The protective resistance 18 is connected across the series cathode circuit for preventing sudden rush of current byreason of condenser discharge or variation in load. This resistance protects the filaments of the tubes in case one of the tubes is removed from its socket. I have found that if a tube is removed it causes a sudden rush of current on account .of the condenser-discharging, which has often 'caused someof the other tubes to burn out. The resistance 18 absorbs any rush of 1. An amplification systemA comprising in combination a plurality of electron tubes` each having a cathode, an anode and a control electrode, an input circuit for each of said tubes including said cathode and control electrode, an output circuit for cach of said tubes including said anode andcath rconnections including a filter system between saidresistance"net-work and sald rectlfymg means, a palr of electron tubes having d1- vided input circuits-coupled with the output 4circuit of the last electron tube of the series,

` a series circuit including the cathodes of said first mentioned electron tubes and a portlonbf' saidresistance .network in shunt withv the space discharge path of said pair of electron tubes, connections for heating the cathodesof said pair of electron tubes from alternatingv current, and means connectedv in series with the control electrodes of said pair of electron tubes for eliminating the hum of alternating curr-ent in said receiv,` ingsystem.

2. An amplification system comprising in combination a plurality of electron' tubes each having a cathode, an anode and a control electrode, an input circuit for each of said tubes including said cathode and control electrode, an output circuit for each of said tubes including said anode and cathode, means interlinking the output circuit of cach of said tubes with the input circuit of a succeeding tube, a source of alternating current, means for rectifying said current, a resistance net-Work, connections including a filter system betweensaid resistance -netfwork and said rectifyin means, a pair of electron tubes having ivided inputeircuits coupled with the output circuit of the last tube of the series, a series circuit including the cathodes ofl said first mentioned electron tubes and a portion of said resistance network in shunt with the space discharge path of said pair of electron tubes, means for independently energizing the cathodes of said pair of electron "tubes, and connections between said resistance network and the anodes of'said firstpmentioned electron tubes for deriving differing potentials for the anodes of said first mentloned electron ltubes.

3. An amplification system comprising in .combination a pluralityiof electron tubes -with. the out ut circuitof one tube interconnected across the output circuit of one of said last mentioned tubes, a series circuit including the filament electrodes of a numberof said tubes, said series circuit being connccted in series with a portion of said resistance network whereby the current supply to said 'filament electrodes and the output circuit ot' said tube of larger power capacity is .governed by Said resistance network.

others of said tubes, a resistance network, a

series circuit containing the filament electrodes of the tubes' of less power capacity thausaid first mentioned tube, and a circuit including the plate electrode of said larger power capacity tube connected in series with .a portion of .sind resistance network, said resistance net-work being shuntefl across the plate circuit of said larger capacity tube.

5. An amplification system comprising in combination a plurality of electron tubes with the output circuit' of one tube interlinked with lthe input circuit of a succeeding tube, a pair of electrony tubes having their' input circuits coupled with the output cir-- cuit of said first mentioned tubes, each of, said tubes having grid, filament and plate electrodes said pair of electron tubes having larger power capacity than said first mentioned tubes, an impedance network, and a series circuit including the filaments of said first mentioned tubes in series with a 'arallel 'connection between' a portion o said impedance network and the plate electrodes of said larger power capacity tubes.

6. An amplification system comprising in combination a plurality of electron tubes with the output circuit of one tube interlinked with the input circuit of a succeed-` ing tube, each of'said tubes having grid, filament and plate electrodes and at least one ofv said tubes-having larger power capacity than the others of said tubes, a series circuit containino` the filament electrodes of the tubes of less power capacity than 'said last mentioned tube, said series circuit including the' plate electrode of one of said tubes 0f larger power capacity and aresistance network having a portion thereof connected in` shunt with the series circuit including the filament electrodes of the tubes of less power ca acity thanpsaid last mentionedl tube.

.- An'amplification system comprising in combination a plurality of electron tubes with the output circuit of one tube interlinked with the input circuit of a succeeding tube, a pair of electron tubes having larger power capacity than Said first menp tioned electron tubes, each of said tubes havcircuit including the filament electrodes of ing grid, filament and plate electrodes, said said first mentioned electron tubes and a porpair of electron tubes having n larger power tion of said resistance network, and connecl0 capacity than said first mentioned electron tions between said resistance network and tubes, with the plate electrodes thereof conthe plate circuits of said pair oflzuger power nected in parallel. with respect to the plate capacity electron tubes.

current supply, a resistance network, a series ROY S. FISHER. 

